ATOMIC STRUCTURE

Modern Atomic Theory
Rutherford’s Atom • This concept of a nuclear atom show that the nucleus of the atom is composed of positively charged particles called protons and neutral particles called neutrons. • Rutherford also found that the nucleus is apparently very small compared to the size of the entire atom. • The electrons account for the rest of the atom.

Emission Energy By Atoms
• When atoms receive energy from some source— they become excited—they can release this energy by emitting light. • The emitted energy is carried away by a photon. Thus the energy of the photon corresponds exactly to the energy change experienced by the emitting atom.

• An excited atom can release some or all of its excess energy by emitting a photon (a “particle” of electromagnetic radiation) and thus move to a lower energy state.
. The lowest possible energy state of an atom is called its ground state. • The energy contained in the photon corresponds to the change in energy that the atom experiences in going from the excited state to the lower state.

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and the neutron (a neutrally charged particle). • The protons and neutrons occupy the nucleus while the electrons are outside of the nucleus.
.Quantum Numbers
• The atom of any element consists of three basic types of particles:  the electron (a negatively charged particle)  the proton (a positively charged particle).

and each successively higher value of describes a less stable energy state. • Each electron in an atom can be assigned a value of that is a positive integer (n = 1. etc) and that correlates with the energy of the electron.
. 3. • Absorption and emission spectra reveal that this energy is quantized.…. • The most stable energy for an atomic electron corresponds to n = 1. 8. 2. • The quantum number that indexes energy is the principal quantum number (n).Quantum Numbers
• The most important property of an atomic electron is its energy.9.

• The smaller is. the more compact the orbital. an atomic orbital also has a specific shape. • The value of correlates with the number of preferred axes in a particular orbital and thereby identifies the orbital shape.• In addition to size. • A second quantum number indexes the shapes of atomic orbitals.
. • According to quantum theory. These restrictions are linked to energy. orbital shapes are highly restricted. so the value of the principal quantum number (n) limits the possible values of l. This quantum number is the azimuthal quantum number (l).